The incident comes amid mounting tension in the US over the deaths of black men at the hands of police.

There are more than 1000 deadly shootings by police in the US each year, and disproportionate numbers of those killed are black Americans.

Marker showing Baton Rouge location in Lousiana. Photo: Google Maps

Police spokesman Cpl L'Jean McKneely said the officers had been called in after reports that a man selling CDs outside a convenience store had threatened someone with a gun.

Mobile video footage appeared to show two officers wrestling a man in a red shirt to the floor.

One of the officers pinned the man's arm to the floor with his knee and then appeared to pull out his gun and point it at the man.

A voice is heard shouting: "He's got a gun. Gun." Then shots ring out and the camera moves away.

Mr Sterling, a father of five, died at the scene.

Cameron Sterling, Mr Sterling's 15-year-old son, began crying at a news conference as his mother spoke.

"He had to watch this as this was put all over the outlets," Quinyetta McMillon, Cameron Sterling's mother said.

"As a mother I have now been forced to raise a son who is going to remember what happened to his father."

Michael McClanahan, president of the city's local NAACP, which is an African-American civil rights organisation, told reporters Mr Sterling's death was indicative of a greater problem with the "the culture of the Baton Rouge Police Department".